A worker at the International Rice Research Institute prepares seedlings at a research centre south of Manila, in the Philippines. Photograph: Darren Whiteside/Reuters

Codename: C4 rice project. Mission: to modify photosynthesis in rice to boost crop yields. Duration: 15 to 25 years. This might sound like science fiction, but it is already under way at the International Rice Research Institute (IRRI) in the Philippines, where William Paul Quick and his team have been working since 2008 on changing the photosynthesis process in rice from the C3 carbon-fixation mechanism, common to 98% of all plants, to its much more efficient C4 counterpart.

Some 50 species, including maize and sorghum, have completed this step naturally, enabling the plants to devote most of their energy to carbon-fixing, and thus to growth. "At present we are studying how far the cell structures and enzymes required to achieve C4-type photosynthesis are already present in rice and closely related plants," says Nourollah Ahmadi, a rice specialist at France's Centre for International Co-operation on Farming Research for Development. "The aim is to activate the available but as yet inactive cell structures and enzymes and to introduce the ones that are lacking by genetic transformation, drawing on other plants."

This could increase output by as much as 50%, bringing about another green revolution, capable of responding to the foreseeable demand for food in 2050, when there will be 9 billion mouths to feed. Rice is currently the staple foodstuff for more half the world's population, with more than 1 billion people depending on rice farming for their livelihoods. "For every additional billion people, an extra 100m tonnes of rice will need to be produced," says Ahmadi. In contrast, the annual increase in yields has slowed since the 1990s, from 2% to just 1%.

Research into rice now concentrates on creating varieties that are more productive and more resistant to the various forms of stress, caused by disease (such as pyriculiariosis) or environmental factors (flooding, drought, extreme temperatures and high salt concentrations).

"Rice will be one of the cereals most affected by climate change," says Robert Zeigler, the head of IRRI. "So it's vital to prepare production systems and rice growers for change if we want to maintain a certain dynamic." Hopes are consequently high for the programme launched by IRRI and China to sequence the genome of 10,000 of the 120,000 known rice varieties. The first results are due in June.

"Thanks to new sequencing techniques, we can determine the specific features of the genome of any particular variety," says Mathieu Lorieux, a geneticist at France's Development Research Institute (IRD). "Our work then consists in cross-breeding the most useful species to obtain new ones that meet consumer demands and environmental constraints, and are resistant to disease."

Lorieux is taking part in a programme to overcome the sterility barrier between Asian (Oryza sativa) and African rice (Oryza glaberrima), the idea being to develop hybrid varieties combining the former's productivity with the robustness of the latter. He is also working on the plant's architecture, so that each shoot produces more grain.

In 2011 IRRI launched a four-year programme on the Mekong delta, in Vietnam, to add flood and salt-tolerant genes to rice.

"More or less all over the world, the potential yield from rice is about 10 tonnes a hectare, whereas the global average is only 4.5 tonnes," Ahmadi explains. "But the effort required to bridge this gap is increasing all the time."

No transgenic rice varieties are currently being cultivated, but "golden rice", a variety developed a decade ago to have added vitamin-A, did cause controversy. Lorieux is certain we shall one day eat transgenic rice: "If a new disease appears and there are no resistant rice varieties, we shall have to look for a resistant gene elsewhere or maybe make a synthetic gene ... or give up growing rice."